A semi‐empirical low‐latitude ionospheric model

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Abstract
Since current empirical models specifying low‐latitude electron density profiles severely underestimate the daytime plasma density scale‐height and total electron content (TEC) values, a semi‐empirical low‐latitude ionospheric model (SLIM) has been developed which is not only computationally fast, but also more realistic. Electron density profiles (180–1800 km) are theoretically calculated as a function of latitude (every 2° between 24°N and 24°S dip latitude) and local time (every half hour, over 24 hours LT) by solving the time‐dependent plasma continuity equation. Using simple exponential functions, sets of coefficients are then generated which reproduce these individual profiles. The coefficients themselves are easily stored, quickly retrieved and form the basis for a fast, portable, semi‐empirical computer code. This paper describes briefly the input parameters used to theoretically calculate the profiles and the procedures used to generate the coefficients. The SLIM profiles are compared with the Chiu and Bent empirical models for equinox, solar maximum conditions, while calculated 6300 Å airglow intensities and TEC values are compared with available observations. The SLIM profiles, their coefficients, TEC and 6300 Å airglow intensities are available in tabular and computer formats.